Part of the difficulty of proving any scientific theory is due to the inductive nature of scientific reasoning, at least, in the empirical sciences. One makes repeated observations, and from those observations, draws inferences. Inferential reasoning, as David Hume points out, provides us with probability, but never certainty. (We’ve seen this truth demonstrated, most recently in the news, with the Casey Anthony trial.)
Asking the evolutionist to prove that the theory of evolution is true, if by “prove” one means give an apodictic demonstration, puts her in a similar position to some theists who are asked to prove that God exists. Arguments can be given, but because the conclusions are inferences, objections can always be raised by skeptics.
This chapter ultimately raises important questions about the nature and limits of inductive reasoning. At what point does a scientific argument provide “proof beyond a reasonable doubt” and who gets to determine this? But I am moving ahead of myself.
In one sense, that evolution occurs is incontrovertible. Over time, breeding, genetic mutations and natural selection give rise to the expression of new biological features and traits. Giberson and Collins correctly explain that the debate is really about the scope of this these changes. Can the changes we see happening within a given species accumulate to give rise to a new species? Or more technically, “Does the uncontroversial fact of microevolution provide evidence for the complex and controversial claims of macroevolution” (45)?
Evolutionists claim that “[i]f a population of some species undergoes a substantial number of such changes, it can eventually turn into a new species, a process called speciation” (36). These changes are cumulative, occurring very slowly and in tiny, incremental steps—over millions of years. Admittedly, such vast spans of time are difficult to imagine, and this a major reason people ridicule and reject the possibility. The authors suggest, however, “We have to distinguish between challenges to our imagination, which have trouble conceptualizing slow processes that take millions of years, and challenges to nature, which have no such limitations” (46).
This is why issues of chronological dating of geological formations figure so significantly in debates about evolution; the theory becomes more plausible as longer spans of time are allotted for it to take place. Chapter 2 will deal with the issues involved in trying to determine the age of the universe/earth. This chapter focuses mainly on evidence for evolution from the field of genetics. The mapping of the human genome, along with the genomes of other vertebrates, has revealed striking similarities between the DNA of humans with each other, as well as other living vertebrates. This, according to the authors, is evidence for common biological ancestry.
One obvious objection to this line of reasoning is that similarities in genetic markers point to a common creator. God could have used the same DNA patterns for all the animals God created, just as a car manufacturer might put common components in the different cars it produces. The authors argue, however, that the details of DNA analysis have “ruled out that conclusion” (43). The example that they mention twice is the inability of humans to produce vitamin C. Unlike most other mammals, humans must consume vitamin C as a regular part of their diet or they develop scurvy. The cause of this deficiency is “a degenerated copy of the gene that makes the enzyme for synthesizing vitamin C” (43). More than half of the coding sequence needed to produce the requisite enzyme has been lost. This would mean that God is responsible for inserting a broken piece of DNA in the human genome. “This,” the authors conclude, “is not remotely possible” (43).
In other words, why would God create humans with only half of a genetic coding sequence? It makes more sense to think that humans have lost an original ability to produce vitamin C through a prolonged process of genetic mutation and natural selection, i.e. evolution.
This, the skeptic will point out, hardly indicates a change from one species to another. It’s entirely possible that this is merely an example of change within a species, i.e. microevolution. But how then does one explain that this is a shared inability humans share with other primates? This suggests the inability to produce vitamin C is a common inherited trait rather than a change within an individual primate species.
But perhaps not. Perhaps this suggests parallel paths of degenerative mutations that are taking place within two separate species. This brings us back to my original point about the limitations inherent in inductive reasoning; it can’t give us the certainty we want. So who gets to determine which inferential conclusions are more reasonable than others?
The answer simply is consensus.
Giberson and Collins place a high degree of trust in the established, consensus views of the scientific community, claiming:
“When there is a near-universal consensus among scientists that something is true, we need to take that seriously, even if we don’t like the conclusion. We don’t have to accept everything blindly, of course, just because scientists believe it, but we should demand compelling reasons for rejecting such a consensus” (29).
In other words, the conclusions of the scientific community are to be generally trusted and compelling evidence is needed to reject the consensus view, not to accept it. The burden of proof is with dissenters who must present an alternative theory that better explains the evidence.
This goes against the instincts of those who look to the scientific establishment with a jaundiced eye. In some Christian circles it is associated with humanism and atheism. The instinctual thing to do when one encounters the views of someone, or an entire community of people that goes against what one believes is to react in fear—to attack the perceived threat and attempt to annihilate it, or to dogmatically defend one’s own position. However, what is instinctual is not is rational, nor is it spiritual; rather, both reason and faith call for the opposite—an attitude of intellectual humility and charity.
Scientific theories with broad consensus and support should be a significant epistemic consideration for anyone seriously inquiring into a given issue. Cavalier dismissals of the views of an entire highly-trained, well-respected community by impugning the intelligence, moral integrity, or spirituality of individuals will look desperate and unreasonable to the outside observer. Beyond this, to suggest that the entire scientific community is supernaturally deceived while affirming divine guidance for one’s own pet interpretation of Scripture is arbitrary and creates an intellectual chasm that makes conversation impossible.
Those who will appeal to theology to resolve this debate will find that the Christian scriptures clearly affirm that God is both the creator of the world, which would include the rational minds that humans use to find their way in that world. As Giberson and Collins aptly point out, science requires:
Christians believe that scientific reasoning, as limited as it is, is ultimately a gift from God, so maligning it is tantamount to maligning God.
Before moving to critique, which should never be mixed with or substituted for with insults, the creationist should be sympathetic to the plight of the evolutionist who uses the same limited inductive reasoning skills that many theists use to determine that God exists. Another way of saying this would be that we should take Jesus seriously when he says, “Do unto others as you would have them do unto you” (Matthew 7:12).
So does one have to believe in evolution, as the title of this chapter asks? I don’t think this chapter alone provides sufficient evidence to answer the question in the affirmative. It raises a series of other important issues and questions, though, and I think that the authors have provided sufficient reasons to seriously, honestly, and charitably inquire into that issue in the upcoming chapters.
—Zane Yi lives in Atlanta, GA. He is a Ph.D. candidate in philosophy at Fordham University.
Here is the introductorary essay about the Summer Reading Group series on the book The Language of Science and Faith. Feel free to get the book, read it and join the discussion. Here is the first post: What is BioLogos?